Slide fence protection system for railroads



Oct. 14, 1947.

w. v. GROBJEAN SLIDE FENCE PROTEGTIOXSYS TEM FOR RAILROADS 2Sheets-Sheet 2 Filed Sept. 22, 1945 H15 ATTORNEY Patented Oct. 14, 1947SLIDE FENCE PROTECTION SYSTEM RAILROADS FOR Wilbur Grosjean, Omaha,Nehru, assignor to The Union Switch and Signal Company, Swissvaile, Pa.,a corporation of Pennsylvania Application September 22, 1945, SerialN0.=B17 ,9-7 7 8 Claims. (01. 246-.121)

Myinvention relates to slide fence protection systems for railroads, andmore particularly to a system of circuits for use in connection withprotection devices such as slide fences or slide detectors such as are.used along the right of way of railroads to detect slides, falling rockor other abnormal conditions.

The principal object of my inventionis the provision of an improvedsystem of circuits suitable for controlling block signaling systems,including those for single track railroads, whereby the operation of aslide detector in any block section due to the encroachment of foreignobjects upon the right of way conditions the signal which governs trainmovements'into the section to indicate stop, if it has been cleared, andalso conditions the corresponding distant signal in the rear thereof toindicate caution, but without interrupting "the line circuits by whichthe signals are normally controlled.

A further object of my invention is the provision of improved means forretaining the-indications of the operation of the slide detector systemuntil after the-obstruction which caused its operation has been removedand the detector circuits have been restored to their normal condition.

A further feature of my invention is the provision of manually operable.keys or push buttons at the locations of the signalsgoverning trainmovements into a block section containing one or more slide detectors,whereby the signal system may be restored to its normal condition by thecrew of a train which has been stopped at asignal as a result of atemporary interruption. of the protection circuits or in the event anObStXllC-r tion which caused the interruption has already been removedand theprotection circuit restored by the maintenance forces.

Another feature of my invention is the provision of means fortransmitting indications of the operation of any slide detector in ablock over the circuits ofthe protection system to a station at one endof the block, from which point a distinctive indication identifying theblock is transmitted to the train dispatchers oflice.

I shall describe one form of apparatus embodying my invention and shallthen point out .the

novel features thereof in claims.

Inthe accompanying drawings, Figs. 1A and 13, arranged side by side,showat the top a single line diagram of the track plan for a typical stretchof single track railway equipped with automatic block signalsforgoverning traihc movements in both directions and having slidedetectorfences at four extended locations within the stretch and identified bythe reference characters ISF to 48F, respectively. The circuits directlybelow those of the track plan are theline circuits for a typicalsignaling system for controlling the signals shown in the track ,p'lan,While the group of circuits below these are the'line circuits by whichthe signal system is governed by the condition of the slide detectorfences in accordance with my invention. The circuits in the lowerportion are the, lighting circuits for the signals controlled jointly'bythe two groups of line circuits above referred to.

The signaling system as shown herein is generally similar tothatdisclosed in a'pending application for Letters Patent of the UnitedStates, Serial No. "501254, filed September 4, 1943, by Henry S. Young,for Railway trafiic controlling apparatus. Inthis system continuoustrack circuits are provided throughout the stretch for governingthesignals in accordance with traflic conditions, the tracks being dividedinto sections by insulated joints. Each track section is provided with aclosed track-circuit identified by the reference character T with anumerical prefix identifying its location. Each track :circuit has atrack battery B, and a normally energized track relay similarlyidentified, at its other end.

The track plan as shown embraces three sections of a single track blockand includes three sets of opposing intermediate signals, comprising thesignals II to 1-4 in Fig. 1A and the signals I 5 and 16 in Fig. 113,each of which is of the three-position color light type having threelamps G, "Y "and R for indicating proceed, :caution and stop,respectively, controlled by a polarized line relay bearing thedesignation HD with identifying prefix.

The plan also includes a short OS section 5T at one end of the block,which containsa track switch 5W connecting the single track stretch witha passing siding. Train movements into section :5T are governed by headblock .signals subject to manual control, these comprising the enteringsignals ELA and -6LB and the leaving signals fiRAiand 'SRB. Each headblock signal as shown is of the Searchlight type having a signal lampadapted to display light of different colors by the operation of apolarized mechanism such as BLAG. V V

In order to simplify the various circuits shown herein, I have shownonly the terminals of the local sources of current for energizing therelays, these beingidentified by the reference characters B and C,designating the positive or supply terminal and the negative or commonreturn terminal, respectively. It is to be understood that eachpolarized signal relay HD or mechanism G operates its contacts to theleft when the lefthand terminal of its winding is connected to thepositive terminal B. thi being designated the normal positioncorresponding to the caution indication of the signal, the reverse orright-hand position corresponding to the proceed indication.

The signal line relays HD are controlled by the track relays TR over atwo wire reversible line circuit system in which the direction oftrafiic is established and the clearing of the head block signals isgoverned manually from the train dispatchers ofiice by means of acentralized trafhe control system by the operation of code controlledrelays of the polar stick type, such as the trafilc direction relay BLFSand the signal control relay BLHS, shown in Fig. 1B.

A directional stick relay such as the relay HS is provided for eachintermediate signal to control the polarity of the current supplied tothe line relay for the next signal in the rear in accordance with thewell known absolute-permissive scheme of operation.

The signal lamps for the intermediate signals are normally dark, butbecome lighted upon the approach of a train by the release of anapproach relay AR which is included in the line circuit in series withthe relay HD for the signal in the rear. As shown, the line circuitsystem is set up for trafiic movements from left to right with thecontacts of the trafltlc relay BLFS and of the similar relay at theopposite end of the block in their left-hand positions, and with relayllHD energized in the normal direction, with relays ISHD, l5I-ID andGLHD energized in the reverse direction and with all of the approachrelays AR energized.

The slide detector fences SF may be of any suitable type and aretherefore shown only diagrammatically herein. These may be, for eX-ample, of the type shown in Letters Patent of the United States No.2,187,518, issued January 16, 1940, to William C. McWhirter, for Circuitcontrollers. For an understanding of my invention, it will suffice topoint out that each fence is divided into two sections held togetherunder tension by heavy coil springs. A circuit controller such as thecontroller ICC for the slide detector fence ISF is mounted in a suitablehousing located between the sections and. comprises a set of fourcontacts a, b, c and d which are normally held closed by a latch. Twotrip rods for releasing the latch are attached to the adjacent sectionsof the fence, the arrangement being such that a lateral displacement ofthe wires of either section of the fence due to a slide, falling rocks,or the like, will trip the latch and open the four contacts.

A drop annunciator is also provided as explained in the patent by meansof which a colored disc or plate is exposed to indicate in which of thetwo fence sections the displacement occurred. The contacts remain openeven though the obstruction is removed, but after the fence has beenrestored to its normal condition the contacts may be latched closedmanually by the maintainer, the operated drop annunciator being restoredto its normal position at'the same time.

Contacts at and b of each circuit controller such as ICC are included ina stick circuit for a normally energized slide detector relay, such asthe relay IZSD, I4SD or IBSD, located at one end of the block sectionwithin which the slide detector fence is located, and each such relaycontrols a repeating relay such as the relay D, I5SD or 6LSD, located atthe other end of the block section, over contacts 0 and d of the fencecircuit controller. Any displacement of either section of the fencewhich is suflicient to release the circuit controller latch and open itscontacts therefore releases the relays SD at both ends of the blocksection. A contact 0 of each relay SD is included in the circuit for thelamp or mechanism for the adjacent signal governing traffic movementsinto the block section, which contact is operated to condition thesignal to indicate stop when relay SD releases, Each relay SD also haspole changer contacts 6 and f in the signal line circuit as illustratedby relay i3SD, for example, by which the polarity of the currentsupplied to relay IEHD is changed from reverse to normal when relay I3SDreleases, to condition the signal [5 which governs the movement oftrafiic approaching the location of relay I3SD to indicate cautioninstead of proceed. A push button PB at each signal location and anauxiliary line relay Z, and back contacts 0 of the track relays providemeans whereby the slide detector stick relays may be picked up followingthe removal of an obstruction and the resetting of the contacts of thecircuit controller CC in their closed position.

Each repeating relay such as relay ISSD or I5SD controls the polarity ofthe current supplied to the slide detector repeating relay such as relayISSD or IBLSD for the next section at the right, providing a system ofcascade connected circuits by which the opening of any of the slidedetector circuit controllers is indicated at the C. T. C. station at oneend of the block either by the release of the neutral contacts of or bya reversal of the polar contacts of the slide detector repeating relayBLSD at that location. From this station the indication is transmittedto the dispatchers office to release an indication relay such as therelay llSDK to light a lamp E on the operators control panel. Usuallythis indication is transmitted to the ofiice over an intermittentlyavailable channel of the code type communication system, but forsimplicity this is represented in the drawing by the equivalent directwire circuit, such as would be used if the distance were relativelyshort.

The signal system is shOWn in the drawings as set up for trafficmovements from right to left, the code controlled relay fiLFS and asimilar relay at the opposite end of the block having been 0perated toclose their left-hand contacts. Relay Ill-ID, for signal ll, occupiesits energized position as shown and a connection to terminals B and C atcontacts a and b of relay l IHD energizes relay ISHD in the reversedirection over line wires -2l and 22, to condition signal l3 to indicateproceed. A connection to terminals B and C over the pole changercontacts 6 and f of relay ISSD, contacts a and b of relay I3HD and wires23 and 24 energizes relay IEHD reverse to condition signal 15 toindicate proceed, and a similar circuit controlled by relays 158D andI5HD over wires 25 and 26 energizes relay GLHD reverse. When switch 5Wis locked normal a switch indication relay ENWP is energized and if thecode controlled relay BLHS is reversed by the central office operator,the mechanism BLAG is energized to condition signal 6LA to indicatecaution or proceed over a, circuit including the neutral and polarcontacts of relay ELHD and having a connection to terminals B and C overcontacts a and b of relay GLHHS, contact of the slide detector relayELSD and contact b of the track relay TR. When switch 5W is lockedreverse, a switch indication relay SRWP is energized in place of relaySNWP and the'mechanism BLBG is energized to cause signal 6LB to indicatecaution or proceed in place of signal GLA.

I shall now briefly describe the operations resulting from a trainmovement through the stretch from right to leftwith the protectionsystem in its normal inactive condition. When the train enters section5T, signal BLA or GLB is restored to stop by the release of relay STR.

When the train enters section 6LT, relays BLHD and [EAR are released bythe shunting of the track relay GLTR, and lamp G of the signal l5 aheadof the train becomes lighted over the circuit including back contact aof relay |5AR and front contacts 0 of relays 'ISSD and I5HD. As thetrain advances into section IGT these conditions aremaintained by therelease of relay ISTR and in addition therdirectional stick relay 15S isenergized over a connection to terminal B at the back contact d of relayIBTRand front contact (1 of relay I'5HD.

When the train enters section I 5T, relays ISHD, ISAR and |3AR arereleased by the shunting of the track relay IETR. Lamp G of the signall3 ahead of the train becomes lighted, due to the release of relay I3AR,lamp G of signal I5 is extinguished and lamp R for that signal islighted due to the releas of relay I5HD, and lamp R of the opposingsignal I6 is lighted due to the release of, relay l-GAR. Theseconditions are maintained by the release of relay MTR as the trainenters section MT and when the train vacatessection IBT relay IG'IRpicks up and relays fiLHD and l EAR become energized by current ofnormal polarity over a connection to terminals B and C at contacts b anda of relay [58,

which rela is held energized over a stick circuit comprising aconnection to terminal B at back contact d of relay l5HD. Theenergization of relay IGAR causes signal l6 to become dark, and theenergization of relay GLHS allows signal BLA or GLB to be manuallycontrolled to indicate caution to permit a following train to enter theblock.

Similar conditions prevail with respect to signals l3, l4 and I5 as thetrain advances through sections ,I3T and HT, and when the train vacatessection I 4T, relay I SS is in its energized position allowing relayI5HD to become energized in the normal direction, releasing relay I58and conditioning signal I5 to indicate caution and reversing thepolarity of the current supplied to relay GLHD to allow signal GLA or6LB to indicate proceed.

I shall now assume that a displacement of the slide protection fence [SFoccurs While the system is set up for traflic movements from right toleft as above described, resulting in the opening of the contacts of thecircuit controller ICC to disconnect terminals B and C from line Wires2! and 28 and to open the circuit over line wires 29 and 30 so thatrelays IZSD, l2Z and I3SD release. The dropping of contact 0 of relayI3SD extinguishes lamp G and lights lamp R of signal l3, provided relay|3AR has been released by a train approaching that signal, and thedropping of contacts e and of relay |3SD changes the polar- 6. ity ofthe current'su'pplied over line wires .23 and 24. to operate relay |5HDto from reverse to normal which extinguishes lamp G and lights lamp Y'ofsignal 1:5, provided relay IEAR is released, so that the approachingtrain will receive successive caution and stop signal indications atsignals l5 and I3, assuming of course it has not already passed thesesignals before the displacement of fence I SF occurs.

In addition, the dropping of the pole changer contacts b and d of relayI3SD changes the polarity of the current supplied over line wires 33 and34 to relay ISSD from normal to reverse so that this relay thereuponoperates its polar contacts h and 9 from left to right to eflfect asimilar change in the polarity of the current supe plied over its frontcontacts b and d and line wires '31 and 38 to relay GLSD. The polarcontact h of relay BLSD thereupon opens, transmitting an indication tothe ofiice to release relay I4SDK and thereby causing lamp E to belighted to indicate to the operator that the controller contacts of oneof the slide protection fences lSF-ESF in the block has been opened.

Similar conditions prevail if the displacement of fence ZSF or 38Foccurs, in which case relays MSD, I 4Z and I5SD release. The dropping ofcontact 0 of relay ISSD conditions signal l5 to'indicate stop, thedropping of contacts e and 7 of relay I'BSD changes the polarity of thecurrent supplied to line wires 25 and 26 reverse to normal to conditionsignal ELA or GLB to indicate caution instead of proceed. If the polarcontacts h and :i of relay I 5SD occupy their normal position as shown,the dropping of contacts b and d of relay I5SD reverses relay 6LSDthereby releasing relay l-GSDK to light lamp E. If a displacement offence 48F occurs, relays BSD, IBZ and BLSD release and the opening ofcontact 0 of relay GLSD in the signal mechanism circuits holds signalsGLA and GLB at stop and the opening of contact b of relay GLSD releasesrelay l-4SDK to light lamp E.

Returning now to a consideration of the efiect of the displacement ofthe fence ISF, it will be evident that if the trouble is not correctedby the maintenance forces before a train reaches signal I 3 the trainwill be stopped at that signal. After obtaining authorization from thedispatcher, the train will continue through section l2-|3 at slow speed.In the event the trouble is corrected and the contacts of controller ICCare latched closed while the train occupies section I3T but before itenters section I2T a circuit is completed from terminal B at backcontact 9 of relay |3SD to terminal C of the source at that locationover back contact 0 of the track relay I3TR, the line wires 29 and 30and back contact b of relay I 2SD through the winding of the slowrelease relay I2Z, which relay assumes its energized position closingits contact a to complete a pick-up circuit for relay I'2SD over wires27 and 28. If the trouble is corrected after the train enters sectionIZT, relay IZSD is picked up directly over back contact a of the trackrelay IZTR. In either case relay IZSD will assume its energized positionand as soon as the train vacates section I31,- relay |3SD will becomeenergized over the circuit including front contacts I) and d of relayI2SD,'line wires 29 and 30 and front contact 0 of relay I3TR.

In the event the trouble is not corrected while the block section I2-l3is occupied by the train but is corrected subsequently, the nextfollowing train will be stopped at signal I3. The train crew will 'thenoperate the push button I3PB at that location, therebycompleting acircuit for relay NZ to reenergize relays IZSD and 'I3SD as abovedescribed, whereupon the indication displayed by signal it will changefrom stop to caution or proceed and the train may resume its movementthrough the block. It will be noted that a stick circuit is provided forrelay I3SD including its own front contact a which serves to prevent itsrelease due to the opening of front contact of relay I3TR.

The protection system may also be restored to normal in the manner justdescribed in the event relay IZSD is released due to any temporaryinterruption of its stick circuit not due to the operation of thecontroller ICC, the system being self-restoring if the duration of theinterruption is less than the release period of relay I2Z. In eachinstance when relay I2SD becomes energized, relay ISSD is reenergizedand the polar contacts of relays lESD and GLSD assume their normalpositions, whereby the indication relay l-4SDK is released and lamp E onthe operators control panel is extinguished.

With traffic movements from right to left set up as above described, theopening of the contacts of either of the circuit controllers 2 CC or 300due to the displacement of oneof the slide protection fences ZSF or 35Fin block section l3l5 or the opening of those of controller 400 due tothe displacement of the fence 4S1 places the system in a conditioncorresponding to that described, and its restoration to normal may beeffected by similar operations as will be obvious from a considerationof the drawings.

In signaling systems of the reversible line circuit type as shownherein, the line circuit system is used not only to govern the signalsbut also to control trafiic direction indicating and locking apparatusat the control office and to govern the operation of electric switchlocks which are provided for the protection of outlying hand throwswitches, as is explained in the Young application hereinbefore referredto. Inasmuch as the operation of the protection system of my inventiondoes not interrupt the continuity of the reversible line circuit system,these additional functions of the system are in no way interfered with,as will be readily apparent. Furthermore, the operation of thedirectional stick relays S as required to effect the clearing of thesignals for a following train is not interfered with by the operation ofthe protection system, as would be the case if the line relays I-ID werereleased by the detector relays SD or if the contacts of the controllersCC were included in the signal line circuits.

I shall now assume that the operator reverses the traflic direction toclear the signals which govern movements from right to left through theblock. This may be accomplished when the block is vacant by reversingthe traffic relayfiLFS and also a similar relay at the left-hand end ofthe block to release relay i iI-ID, thereby releasing relays ISHD, ISHDand ELI-ID successively, the release of relay l5I-ID completing acircuit for relay IBHD over wires 25 and 26 and the right-hand contactsa and b of relay ELFS, this circuit also including a contact e of anapproach lockin relay ELAS which is energized when signals SLA and 6L3are at stop, contacts a and b of a pole changer relay tPtPC controlledby signal ERA and a front contact a of relay 5TB. Relay iBHD is therebyenergized in the normal or reverse direction to efiect the successiveenergization of relays ED and IZHD and the various approach relays ARalso become energized. In view of the symmetry of the circuits, it willbe evident that the operations resulting from train movements from leftto right through the stretch when the protection system is in its normalinactive condition will be similar to those already described, andconsequently these will be understood without further description. Thecontrol of the signals for the left to right direction by the detectorrelays SD is also similar to that already described, and likewise therestoration of the protection system by the track relays. For left toright movements, the relays IZSD etc. may be reenergized by theoperation of a push button such as I2PB at the same location, as isobvious.

Although I have herein shown and described but one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a protection system for railroads, a stretch of railway track, aprotection device adjacent said stretch, a track circuit for saidstretch having a normally energized track relay, a circuit controllerhaving contacts arranged to be manually closed and to open when theprotection device is displaced from a normal position, a signal at eachend of the stretch for governing trafiic movements into the stretch,line circuits for clearing each signal including front contacts of saidtrack relay, a normally energized detector relay adjacent one of saidsignals, a repeating relay adjacent the other signal controlled overfront contacts of said detector relay, a pick-up circuit for thedetector relay including a back contact of said track relay and saidcircuit controller contacts, a stick circuit for the detector relayincluding its own front contact and said circuit controller contacts,and means responsive to the release of the detector relay and of itsrepeating relay for causing the display of stop indications by saidsignals irrespective of the condition of said line circuits.

2. In a protection system for railroads, a stretch of railway track, aprotection device adjacent said stretch, a track circuit in said stretchhaving a normally energized track relay, a circuit controller havingcontacts arranged to be manually closed and to open in the event theprotection device is displaced from a normal position, a signal forgoverning trafiic movements into the stretch, a line circuit includingfront contacts of said track relay for clearing the signal, a normallyenergized detector relay, a pick-up circuit for the detector relayincluding a normally open manually operable contact adjacent the signaland said circuit controller contacts, a stick circuit for the detectorrelay including its own front contact and said circuit controllercontacts, and means responsive to the release of the detector relay forcausing the display of a stop indication by said signal withoutinterrupting said line circuit.

3. In a protection system for railroads, a stretch of railway track, aprotection device adjacent said stretch, a track circuit in said stretchhaving a normally energized track relay, a circuit controller havingcontacts arranged to be manually closed and to open in the event theprotection device is displaced from a normal position, a signal at eachend of the stretch for governing traffic .movements into the stretch,line circuits for clearing each signal including front contacts of saidtrack relay, a normally energized detector relay and a slow releaserelay-adjacent one of the signals, a repeating relay adjacent the othersignal controlledover apair of line wires by front contactsofsai'ddetector relay, a pick-up circuit for saiddetector relayincluding a normally open manually operable contact adjacent thereto, asecond pick-up circuit for said detector relay including a front contactof said slow release relay, and a stick circuit for said detector relayincluding its own front contact, all of said relay circuits includingsaid circuit controller contacts, an energizing circuit for said slowrelease relay including a normally open manually operable contact at thelocation of said repeating relay, a back contact of said repeatingrelay, said line wires and a back contact of said detector relay, andmeans responsive to the release of said detector relay and of itsrepeating relay for causing the display of a stop indication by saidsignals irrespective of the condition of said line circuits.

4. In a protection system for railroads, a stretch of railway track, aprotection device adjacent said stretch. a track circuit in said stretchhaving a normally energized track relay, a circuit controller havingcontacts arranged to be manually closed and to open in the event theprotection device is displaced from a normal position, a signal at eachend of the stretch for governing trafilc movements into the stretch,line circuits for clearing each signal including front contacts of saidtrack relay, a normally energized detector relay adjacent one of thesignals, a repeating rela adjacent the other signal controlled by frontcontacts of said detector relay, a manually operable key adjacent eachsignal, a pick-up circuit for said detector relay including said circuitcontroller contacts and contacts closed in response to the operation ofeither of said keys, a stick circuit for said detector relay includingits own front contact and said circuit controller contacts, and meansresponsive to the release of said detector relay and of its repeatingrelay for causing the display of a stop indication irrespective of thecondition of said line circuits.

5. In combination with a stretch of railway track divided into blocksections, signals at the ends of said sections for governing trafficmovements through the stretch, a system of cascade connected polarizedline circuits extending through said stretch for controlling saidsignals to cause the display of caution or proceed indications inaccordance with the polarity of the current supplied thereto, aprotection device ad- J'acent the tracks of one section of said stretch,a circuit controller having contacts arranged to be manually closed andto open in the event the protection device is displaced from a normalposition, a detector relay and a normally open manually operable contactadjacent the signal governing trafiic movementsinto said one section,pick-up and stick circuits for the detector relay including saidmanually operable contact and a front contact of the detector relay,respectively, both of said circuits including said circuit controllercontacts, means including contacts of the detector relay in a localcircuit for the adjacent signal for causing the display of a stopindication thereby without interrupting the line circuit for such signalin response to the release of said detector relay, and means includingother contacts of said detector relay for governing the polarity of thecurrent supplied to the line circuit for the next signal in the rearthereof to condition such signal to display a caution indication inresponse to the release'of said-detector relay.

6.. In a protection system for. railroads, a stretch of, railway track,a protection device adjacent said stretch, a track circuit for saidstretch having a normally energized track relay, a circuit controllerhavingicontacts arranged to be manually closed and to open when theprotection device is displaced from a normal position, a signal forgoverning trafiic movements into the stretch, a control circuit forclearing the signal including front contacts of said track relay, anormally energized detector relay, a slow release relay, ick-up andstick circuits for the detector relay including a front contact of theslow release relay and of said detector relay, respectively, both ofsaid circuits including said circuit controller contacts, a repeatingrelay adjacent said signal, a circuit for said slow release relayincluding back contacts of said detector relay, of the repeating relayand of the track relay, a circuit for the repeating relay includingfront contacts of said detector relay and also including a front contactof the track relay bridged by a front contact of said repeating relay,and means controlled by said repeating relay when released for causingthe display of a stop indication by said signal irrespective of thecondition of said control circuit.

7. In a protection system for railroads, a stretch of railway track, aprotection device adjacent said stretch, a track circuit for saidstretch having a normally energized track relay, a circuit controllerhaving contacts arranged to be manually closed and to open when theprotection device is displaced from a normal position, a normallyenergized detector relay controlled by said contacts, a first signal forgoverning traiiic movements into said stretch, a second signal forgoverning traific approaching said first signal, a line relay controlledover front contacts of said track relay for controlling saidfirstsignal, a directional stick relay, a pick-up circuit for said stickrelay including a front contact of said line relay and a contact closedby an approaching train. a stick circuit for said stick relay includinga back contact of said line relay, means controlled by the directionalstick relay when energized for conditioning the second signal toindicate caution, means controlled by the line relay and the detectorrelay for conditioning the second signal to indicate proceed when bothsaid relays are energized and to indicate caution when only said linerelay is energized. and means controlled by said detector relay whenreleased for conditioning said first signal to indicate stopirrespective of the condition of said line relay.

8. In combination with a stretch of railway track divided into blocksections, signals at the ends of said sections for governing trafiicmovements through the stretch, a protection device in each section, acircuit controller for each device having contacts which open when thedevice is displaced from a normal position, a normally energizeddetector relay for each section controlled by the circuit controller forthe device in such section, means responsive to the release of each suchrelay for causing the display of a stop indication by the signal whichgoverns trafiic movements into such section, an indication relaycontrolled by one of said detector relays in accordance with thecharacter of the current supplied thereto, indication means at a controloffice controlled by said indication relay, and means for controll ngsaid detector relays in cascade by governing the character of thecurrent supplied to 11 one or more of such relays whereby said indica-REFERENCES CITED tion relay is actuated to one position when an of Thefollowing references are of record in the the detector relays areenergized and to another fil of this patent: position in response to therelease of any one of said relays a 5 UNITED STATES PATENTS Number NameDate WILBUR V. GROSJEAN. 2,232,379 Field Feb. 18, 1941

